The silicon nitride
passivated copper-metallized airbridges had been successfully integrated on the
low noise PHEMT (Pseudomorphic High Electron Mobility Transistor) using WNx
as the diffusion barrier between copper and the conventional gold based
electrodes.40 A PecVD (Plasma Enhanced Chemical Vapor Deposition) silicon
nitride was used for copper airbridge passivation to avoid the copper
oxidation.The 0.25x160mm2
copper-airbridged PHEMT device shows a transconductance of 480mS/mm and a noise
figure of 0.76 dB with an associated gain of 10.4 dB at 12 GHz.The decide performance is comparable to
devices with gold-metallized airbridges.The performance did not degrade after annealing at 250oC for
20 hours.This study shows promising
results for copper metallization of GaAs devices in the future.